1. Field of the Invention
The present invention relates to implantable vascular access devices used in the delivery and/or withdrawal of fluids to and from the body and more particularly relates to a self-sealing device which permits intermittent vascular access.
2. Description of the Prior Art
Conventional vascular access devices are surgically implanted under the skin to allow for intermittent access to a selected vascular structure, such as an artery or a vein, for introducing and/or withdrawing fluids to and from the selected vascular structure. Typically, such devices generally include an interior chamber having an outlet opening connected via a cannula to a vascular structure within the body and a penetrable membrane which serves as a cover for the interior chamber of the device. The penetrable membrane or septum is comprised of a material, such as silicone rubber, which automatically reseals itself after being penetrated by a hypodermic needle or a needle introduced catheter.
In operation, a needle passes through the skin and through the penetrable membrane into the interior chamber allowing fluid to be injected into the chamber and expelled through the cannula into the selected vascular structure or, conversely, fluid may be withdrawn. The advantages of an implantable device over acute catheter procedures include reduced infection, easier patient maintenance and improved aesthetics. Typical implantable vascular access devices are shown in U.S. Pat. No. 5,318,545 to Tucker and U.S. Pat. No. 5,755,780 to Finch, Jr. et al.
The advancement of modem hemodialysis procedures have brought with it the development of vascular access devices for the purpose of acquiring and returning large quantities of blood for passage through a hemodialysis unit. To facilitate adequate dialysis flow rates, relatively large diameter needles and/or catheters in the range of 14 gauge or higher are required. A major drawback of conventional vascular access devices, particularly those used in hemodialysis procedures, is the deterioration of the rubber membranes as a result of repeated penetration with such large gauge needles. Additionally, typical vascular access devices provide for only one needle port resulting in chronic breach of the skin at the same location. This in turn results in increased skin trauma and possible infection.
Accordingly, it is desirable to provide a vascular access device which can withstand multiple insertions with a large diameter needle and which provides reduced skin trauma and easier patient maintenance.
It is an object of the present invention to provide a vascular access device which can withstand a high number of large gauge needle insertions without deterioration.
It is another object of the present invention to provide a vascular access device which is easily subcutaneously manipulated and which prevents the escape of fluids from the device.
It is yet another object of the present invention to provide a vascular access device having multiple needle ports thereby reducing the skin trauma caused by repeated needle sticks at the same location.
It is still a further object of the present invention to provide a vascular access device suitable for hemodialysis procedures which incorporates two interior chambers into a single body.
In accordance with one form of the present invention, a vascular access device generally includes a housing having an inlet, an outlet, an interior chamber defined therein and a valve positioned between the inlet and the interior chamber. The valve is movable between an open position, in which fluid can flow between the inlet and the interior chamber, and a closed position in which the valve occludes the inlet. Preferably the valve comprises an elongate member having a through-hole formed therein which aligns with the inlet when the valve is in the open position. One or both ends of the elongate member protrudes through the housing and is palpable through the skin of the patient. The elongate member is resiliently urged to its closed position by a spring and is opened by subcutaneously pressing the end of the member protruding through the housing.
The present invention may include any combination of multiple inlets, outlets and/or interior chambers. In the preferred embodiment, the housing includes two separate interior chambers suitable for the inflow and outflow of a typical hemodialysis procedure. The device further includes multiple inlets in fluid communication with each interior chamber. Several elongate members are moved simultaneously to an open position by a single push button protruding through the outer surface of the housing. Each elongate member includes throughholes which are aligned with respective inlets when the push button is depressed to move the elongate members to their open position. When the button is released, a spring urges the elongate members to their closed position thereby occluding the inlets. Each interior chamber is in fluid communication with an outlet which is connected to a selected vascular structure by means of a cannula for permitting fluid communication between the vascular structure and the interior chamber of the device.
A method for accessing a vascular structure is provided which includes the steps of surgically implanting a device as described above, connecting one end of a cannula to the outlet of the device and another end of the cannula to a selected vascular structure, subcutaneously manipulating the valve of the device for permitting fluid communication between the inlet of the device and the selected vascular structure and introducing a needle or a needle-introduced catheter through the inlet opening to access the selected vascular structure.
A preferred form of the vascular access device, as well as other embodiments, objects, features and advantages of this invention will be apparent from the following detailed description of illustrative embodiments thereof which is to be read in conjunction with the accompanying drawings.